Method and apparatus for drying a wet web



Oct. 10,1967 E. T. BRYAND ETAL 3,345,756

METHOD AND APPARATUS FOR DRYING A WET WEB Filed Oct. 23, 1965 2 Sheets-Sheet l I04 I26 7 ,5 I25 7 I28 I I2? I34 INVENTORS.

EDWARD T. BRYAND BY EDWARD s. PEABODY Oct. 10,1967 E. BRYAND ETAL METHOD AND APPARATUS FOR DRYING A WET WEB Filed 001;. 23, 1965 I 2 Sheets-Sheet 2 75 F1 2 H Fi 3' 72 e a c 0 20 65 /99 I02 mm g 99 r35- INVENTORS. EDWARD T. BRYAND 45 EDWARD G. PEABODY I25 I2! I35 BY |2o p mug, I 19. I38 A I' TORNEYS United States PatentO 3,345,756 METHOD AND APPARATUS FOR DRYING A WET WEB Edward T. Bryand, South Portland, and Edward G. Peabody, Gorham, Maine, assignors to Metal-Tech Inc., Biddecford, Maine, a corporation of Maine Filed Oct. 23, 1965, Ser. No. 509,676 4 Claims. (Cl. 3423) ABSTRACT OF THE DISCLOSURE A drum, having a strip honeycomb surface which is 85% or more of apertured area is rotatable in an enclosure divided into a positive air pressure compartment on the delivery side of a blower and a negative air pressure compartment on the influent side of the blower. Heat is supplied to the positive air currents and a predetermined percentage of moisture laden air is continuously discharged from the enclosure. Adjustable sleeve deckle means is provided within the honeycomb drum, operable from outside the enclosure during rotation of the drum to conform effective drum width to web width.

This invention relates to an improved method and apparatus for drying a wet web at relatively high speed.

The invention is especially intended to take the place of conventional dryers, now used for drying textile fabrics, paper or similar porous webs, such dryers usually training the web around twenty or thirty steam-heated, smoothfaced cylinders, or steam cans, being costly and occupying considerable floor space. A single dryer apparatus of this invention may be used to pre-dry a moist textile fabric, prior to tentering and final drying, to eliminate free moisture in the fabric. The predrying permits the tenter to increase its speed of operation. When complete drying is desired, a battery of dryers of this invention may be used, for example with the first unit applying hot air at about 500 F. to remove about half of the moisture from the web and the second and third dryers applying hot air at about 300 F. to each remove about one quarter of the remaining moisture in the web.

It has heretofore been proposed to advance a porous web over a perforated roll, within a hot air circulation enclosure, for drying the web, but the perforations in such rolls have provided an apertured area of only about fifty percent. Thus the roll has created a substantial pressure differential, from one face to the other, before the web is supported thereon. The addition of the resistance of the roll surface, and the resistance of the fabric, to the passage of air has required a relatively high pneumatic head to circulate the hot air through both the fabric and the roll surface.

In this invention, the roll surface is at least 85% apertures, the surface being rigid by reason of the thin, honeycombed strips which support one face of the web. The apertured roll surface has a pressure differential of less than one percent. The inside of the honeycombed surface is smooth and true to properly seal with adjustable sleeves and the outside of the honeycombed surface is smooth and true to properly support one face of the web. By substantially eliminating resistance of the roll to passage of hot air, the pneumatic head required to pass air through a web on the surface is governed entirely by the permeability of the web and the head is therefore reduced. The reduced head, however, is still sufficient to circulate a maximum volume of air within the enclosure, and through the web and roll, at a minimum pressure differential and with the hot air passing through the web at high velocity to mechanically, or pneumatically, scrub out the moisture. The moisture, picked up by the hot air from the web, is

, tion, Ser. No. 419,780 filed Dec. 21, 1964. It is charac- 3,345,756 Patented Oct. 10, 1967 recirculated repeatedly through the advancing web, the presence of the moisture in the air increasing its thermal efliciency. During each recycling, a predetermined percentage of the volume of the moist hot air, for example 20%, is discharged from the dryer apparatus preferably to outside the building while an equivalent percentage of new, make-up air is introduced into the apparatus. During rotation, the effective width of the apertured surface of the roll is adjustable to conform to the width of the web and the hot air circulation system is also adjustable to conform to the density of the fabric of the web.

The principal object of the invention is to provide a rugged, low cost, high speed drying apparatus in which one face of a web to be dried is supported on a surface having at least eighty-five percent apertured area so that the surface presents negligible resistance to the passage of hot air through the web.

Another. object of the invention is to eliminate the multiple steam heated dryer rolls of the prior art by supporting a web to be dried on a movable, open mesh Work rigid surface in a mass of low head, high temperature air and circulating the air to cause it to pass through the pores of the web at high velocity and then through the open mesh work surface.

Still another object of the invention is to provide a method for drying wet porous webs on an apertured roll in a hot air environment in which the direction of hot air flow through the web on the roll is reversible, a percentage of the hot moist air is continuously discharged from the environment and the permeability of the web alone controls the speed of drying.

Other objects and advantages of the invention will be apparent from the claims, the description of the drawing and from the drawing in which:

FIGURE 1 is a front elevation, in half section, of the dryer apparatus of the invention;

FIGURE 2 is a side elevation on line 22 of FIGURE FIGURE 3 is a view similar to FIGURE 2, but showing the air flow reversed;

FIGURE 4 is an enlarged, fragmentary front elevation from one end of the hollow roll shaft, showing the deckle adjusting means, and

FIGURE 5 is an enlarged fragmentary side elevation of the device shown in FIGURE 4.

A preferred embodiment of the device of the invention is shown in the drawing wherein the dryer apparatus 20 is supported on the floor 21 of a building having an exterior wall 22. Dryer 20 includes the housing 23, having sheet metal walls supported on a suitable angle framework 24, the walls being relatively thick and sandwich insulated as at 25 to form a closed environment for the circulation of hot air. Housing 23 has a Web entrance 26 preferably in the lower portion of the rear wall 27 and a web exit 28, preferably opposite the entrance, in the lower portion of the front wall 29. The top wall is designated 31, and the side walls are designated 32 and 33.

A movable, open meshwork member 34 having a web supporting surface which is at least and preferably apertured is mounted in the lower portion of the enclosure formed by housing 23. It is believed to be critical that member 34 be in the form of a hollow, cylinder 35 having opposite open ends 36 and 37 and having a honeycomb pattern, of thin metal strips 38, each extending generally radially, to present thin, relatively rigid'edges on the exterior face 39 and the interior face 40 of the cylinder 35. A cylinder such as 35, is now termed a honey-comb roll and may be of the general construction described in the US. Patent 3,100,928 of Aug. 20, 1963, the US. Patent 3,139,375 of June 30, 1964 or in the US. patent applicateristic of such honeycomb rolls, that the meshes, flow conduits or passages 42, between the strips 38, cover at least 85% of the area of the apertured surface 43 of the roll, while the strips are still rigid enough to avoid sag and distortion in supporting a web 44, carried by the roll.

To take full advantage of this characteristic, of the honeycomb roll, a pair of spider heads 45 and 46 are fast to each end of the cylinder 35, the heads being fast to a hollow shaft 47 and the shaft being rotatable in suitable bearings 48 and 49. For the same reason a pair of web guides 51 and 52, preferably in the form of rotatable rolls, are provided below cylinder 35, each closely spaced, about twice the thickness of the web 44, from each other and each spaced about a single thicknesspf the web from the apertured surface 43. The web 44 is thus advanced into housing 23 through entrance 26, thence around roll 52, thence, under predetermined tension, with one web face 53 in intimate contact with, and supported on, at least 350 of the angular distance around roll 35 to substantially enclose the roll as a porous, or permeable, sleeve thereon. The web is then guided around the other roll 51 and out of housing 23 through exit 28.

A pair of imperforate trap doors 54 and 55 are pivoted at 56 and 57 to framework 24, below roll 35 to .form the bottom wall of the housing 23. Each door such as 55 is power opened and closed by a fluid pressure cylinder 58 and piston rod 59, there being a suitable conduit 60 to mill air pressure. The doors 54 and 55 not only permit access to roll 35 for threading of the web 44 therearound but also permit easy insertion, repair, or removal of the roll 35.

Air circulating means 62, is mounted within housing 23, for inducing an air current in the closed, heat insulated environment, or enclosure, therewithin. As shown, means 62 is preferably a pair of blowers 63 and 64 each having an intake 65 or 66, a discharge 67 or 68 and a shaft 69 or 70. Each blower 63, or 64, is driven through suitable pulleys 72 and 73 and a belt 74 by an electric motor 75 or 76, the motors being outside the housing 23 on top wall 31. The blowers 63 and 64 are of a type rated at inches water column and 150 cubic feet of air per minute per inch of dryer face and may be, for example, Buffalo blowers made by Buffalo Forge Co., Buffalo, N.Y., No. 182A, two outlet, 15,000 c.f.m. at 5" SP. Blowers 63 and 64 may be mounted as shown in FIGURES 1 and 2, above roll 35 to direct air downwardly toward the roll surface, out the ends of the roll 35 and back to the blower intakes in a closed unidirectional path. As shown in FIGURE 3 the blowers are so mountable as to be arranged to direct air downwardly into the ends of the roll 35, then out through the roll surface and back to the blower intakes in a reversed unidirectional path. In the latter arrangement the air forms an air cushion under the web, as at 71 in FIGURE 3, to float the web at a spaced distance from the roll face, this being advantageous with wet dyed fabrics. If desired, a single blower of the in-line type, comprising a hollow tubular shell with a fan blade therewithin, could be used as the air circulating means 62, the blower having identical mounting flanges at each end and being bodily removed, reversed, and re-installed in order to reverse the direction of air flow.

Air filters 78 and 79 are provided for each blower in the path of the air discharged from the blowers. Each is of the type having a disposable filter element and is accessible through the access door 80 in front wall 29, for replacement when the element is filled with lint or the like.

Partition means 82 is provided within housing 23, consisting of interior partitions 83 and 84 each having a circular hole 85, or 86, in the lower portion thereof, encircling one end of the apertured surface 43 of roll 35, and extending upwardly to a suitable hole 87 or 88 for receiving either the intake or discharge of the blowers. In the arrangement of FIGURES 1 and 2, the partition means 82 forms a first, or positive, pressure chamber 89,

into which the blowers induce a large volume of air to contact the exposed face 90 of the web trained around roll 35, and a second, or negative, pressure chamber 91, wherein the air is conducted from the interior of the roll 35 out from the ends thereof, back to the intakes of the blowers, the interior of the roll forming part of the cham ber 91.

Air heating means 93 is mounted in housing 23, in the path of the air circulated therein. Means 93 may be a pair of heat exchangers 94 and 95 each having two finned steam coils continuously supplied with p.s.i.g. steam through supply conduit 96 and return conduit 97 to maintain a 300 F. operating temperature. Means 93 may also be in the form of gas fired, infra-red heaters, especially when complete drying is desired and when the dryer 20 is the first to a battery of three such units which treat the web successively. In such case the heaters of the first unit heat the circulating air to about 500 F. to remove about half the moisture when the moisture in the web is initially at room temperature. The second and third dryers, are identical with dr-yer 20, but heat the air only to about 300 F. to remove the remainder of the moisture without damaging the web. In FIGURES 1 and 2 the air heating means 93 is in the first chamber 89, which is the positive chamber, while in FIGURE 3, the chamber 89 has become the negative chamber and chamber 91 has become the positive chamber.

It will we understood that as the web 44 travels through the dryer 20, under the predetermined tension required to draw it around the apertured face 43, for example, at one hundred and fifty feet per' minute the hot air passed through the web and roll becomes saturated with moisture there-by increasing its ability to retain heat and in= creasing its thermal efficiency. To discharge a predeter' mined percentage of the total volume of moist hot air being circulated within housing 23, moist air removal means 99 is provided. As shown, there is an etfiuent port 100 in an inclined upper portion 101 of partition means 82 which connects with an exhaust conduit 102 to direct flow through rear wall 27 to suitable ducting leading to the atmosphere, at a remote distance from dryer 20, pref erably through exterior wall 22 to outside the building. Means 99 is arranged to remove 2025% of the moist air from the total volume of air in dryer 20, there being a suitable damper 103 in conduit 102 for manually, or auto matically, controlling the volume of discharge. A pair of influent ports 104 and 105 are provided, each in one of the side walls 32 or 33 of housing 23 and each on the negative side of the air flow path, to introduce a volume of fresh, dry air from the ambient atmosphere into housing 23 to compensate for the percentage of moist air being continuously discharged therefromsuitable louver, or other damper, controls, 106 and 107 are mounted in the influent ports for manual, or automatic, control thereof in cooperation with damper 103.

Axially slidable sleeve means 109 is provided in dryer 20 to adjust the effective width of the apertured surface 43 of roll 35, to conform to the width of web 44, during rotation of the roll. Means 109 includes a pair of deckles 110 and 111, each having a circular rim such as 112 or 113 closely fitting, and sealing, with the smooth inside face 40 of roll 35 and each connected to the adjacent open end of the roll by telescopable sleeves, indicated at 114 and 115, of imperforate, material such as metal. When roll 35 is, for example, about one hundred inches of face length, the deckles 110 and 111 are arranged to provide the full face length when retracted but to be axially slidable inwardly from each roll end for about twenty-five inches to define a central zone of open apertured face about fifty inches in face length.

It has been found that "the selvedge of a web 44, if of woven fabric is more dense than the remainder of the fabric and that is difficult to dry such a web uniformly thereacross. In this invention, the deckles and sleeves are therefore adjusted axially so that the-deckles are about one half inch outside of the path of the selvedge on each opposite side thereof. Thus hot moist air not only passes through theselvedge but also passes around the selvedge, thereby drying the selvedge at the same rate as the remainder of the fabric.

The deckles 110 and 111 each include a central circular aperture 117 or 118 for receivin the exterior of the hollow shaft 47 of roll 35, the shaft having longitudinal slots 119 and 120 in the wall 121 thereof. Deckle actuating means 122, includes at least one, and preferably two, parallel endless chains 123 and 124, each extending from one end of hollow shaft 47 to the other, and trained around sprockets such as 125, 126, 127 and 128 rotatably mounted in fixed blocks 130 and 131 beyond the ends of the shaft. A reversible electric motor 132, carried on platform 133, is drivingly connected to the shaft 134, carrying the sprockets at one end of the hollow shaft, by drive means 135 to move the chains axially back and forth within the shaft as desired, during rotation of the roll 35. A suitable tab, or spoke, 136 and 137 on each deckle extends through one of the axial slots 119 or 120, with an integral, annular yoke element thereon, for engagement by a lug 138 or 139 on each chain to permit the axially movable, non rotating chains to axially slide the deckles and sleeves as they rotate with roll 35.

In operation, the drying apparatus of FIGURES 1 and 2, continuously conducts a large volume of low pres sure hot moist air current in a closed endless path includ ing air heating means 93, the web 44 advancing through housing 23 on roll 35, the apertured surface 43 the open ends 36 and 37 of roll and the air circulating means 62, the pressure differential between the positive and negative chambers being a factor of the web permeability only and a percentage of hot moist air being continuously replaced by fresh make up air.

If the direction of air flow is reversed as in FIGURE 3, the moist air removal means 99 is formed by the influent ports 104 and 105 so that the positive pressure side of the housing continually dumps, or discharges a predetermined percentage of moist air. Similarly the fresh air supply means is formed by the effluent port 100, so that the negative pressure side of the housing may continually draw fresh dry air from the outside atmosphere.

We claim:

1. The method of pre-drying a wet web of textile fabric to remove free moisture therefrom by the use of a hollow, honeycomb-surfaced, cylinder rotatably mounted below a blower within an enclosure, said method comprising the steps of:

advancing said web progressively through said enclosure with a stretch thereof trained around about 350 of the honeycombed surface of said cylinder while maintaining said stretch in intimate contact therewith under predetermined tension; automatically reducing the effective width of said honeycombed surface within the interior thereof from the exterior thereof to conform with the width of said web, while said roll is rotating;

continuously discharging air downwardly from said blower through said fabric stretch and through said honeycombed surface, into the interior of said cylinder;

continuously heating the said air discharged from said blower, to a temperature of about 300 F. in advance of said fabric stretch to laden the air within said cylinder with free moisture;

continuously withdrawing said moisture laden air from said cylinder and recirculating a predetermined percentage of the volume thereof to the intake of said blower;

and continuously discharging a predetermined remaining percentage of the volume of said moisture laden air, under pressure from the pressure side of said blower, into an atmosphere remote from said enclosure.

2. The method of drying a wet web, having a predetermined permeability, in a hot air environment containing a rotatable cylindrical roll, said method comprising the steps of: 3

providing open ends and an apertured cylindrical surface on said roll, so that the apertured area is at least of the total area of said surface and so that said apertured surface passes a maximum volume of air therethrough with a minimum pressure differential inside and outside of said roll;

advancing said web at predetermined speed through said hot air environment with one face of said web extending around, and supported on, at least 350 of the 360 apertured surface of said roll; circulating the hot air in said environment in an endless path extending from one face of the web, so supported on said roll, to the opposite face thereof to saturate said air With moisture from said web to a predetermined constant equilibrium, continuously withdrawing a predetermined percentage of the total volume of the moisture laden air in said closed environment, to a discharge location remote therefrom, while continuoussly introducing an equivalent volume of unsaturated, make-up air into said closed environment and reducing the effective width of the apertured surface of said roll, during rotation thereof, until the said width is slightly greater than the width of said web in an amount suflicient to pass air around, as well as through, the opposite edges of said web to dry the same in conformity with the rate of drying of the remainder of the web. 3. A drying apparatus for removing moisture from a wet porous web having a predetermined permeability, said apparatus comprising:

a dryer housing having a web entrance and a web exit; an open ended, hollow, cylinder rotatably mounted within said housing, said cylinder having a surface with at least eighty-five percent apertured area, permitting substantially free unimpeded passage of air between said surface and the interior of said roll;

guide means, within said housing, for guiding said web around at least 350 of the angular distance around said roll surface, with one face of said web supported on said surface;

air circulating blower means mounted within said housing for inducing an air current therein; an air heating means mounted within said housing for heating said air to at least 300 F.;

partition means within said housing for conducting said air current in a closed endless path, said path including said air heating means, said apertured roll surface, the web supported thereon, the open ends of said roll and said blower means; the pressure differential between the outside and inside of said roll surface being less than one percent, in the absence of said web, and being controlled by the permeability of said web alone at specific pneumatic heads established by said blower means, and

moist air removal means for discharging a predetermined part of the volume of said circulating air from said housing;

axially slidable sleeve means mounted within said cylin der for reducing the effective Width of said apertured surface from at least one open end thereof toward the centre and means operable from outside at least one end of said roll for actuating said sleeve means during rotation of said cylinder to adjust the cylinder width to the web width.

4. A drying apparatus for removing moisture from a wet porous web having a predetermined permeability, said apparatus comprising:

a dryer housing having a web entrance and a web exit;

an open ended, hollow, cylinder rotatably mounted within said housing, said cylinder having a surface with at least eighty-five percent apertured area, per- Initting substantially free unimpeded passage of air between said surface and the interior of said roll;

guide means, within said housing, for guiding said web around at least 350 of the angular distance around said roll surface, with one face of said web supported on said surface;

air circulating blower means mounted within said housing for inducing an air current therein;

an air heating means mounted within said housing for heating said air to at least 300 F.; I

partition means within said housing for conducting said air current in a closed endless path, said path including said air heating means, said apertured roll surface, the web supported thereon, the open ends of said roll and said blower means;

the pressure difierential between the outside and inside of said roll surface being less than one percent, in the absence of said web, and being controlled by the permeability of said web alone at specific pneumatic heads established by said blower means;

moist air removal means for discharging a predeter- 8 mined part of the volume of said circulating air from said housing;

a pair of telescopable, sleeve assemblies, each mounted within said cylinder to slide between a central zone thereof and the adjacent end thereof;

a hollow shaft on said cylinder, said shaft having at least one endless chain, extending longitudinally therewithin and trained around sprockets at each opposite shaft end, said chain being operably con nected to said assemblies, and

means, outside said cylinder and hollow shaft for moving said chain to slide said assemblies during operation of said dryer apparatus.

References Cited UNITED STATES PATENTS 920,351 5/1909 Layland et a1 341 15 1,601,332 9/1926 Whitehead et a1 34115 2,189,915 2/1940 Mellor et a1. 34122 2,473,629 6/1949 Andrews 3468 2,713,213 7/1955 Bogaty 34--82 3,098,371 7/1963 Fleissner 34115 KENNETH w. SPRAGUE, Primary Examiner. 

1. THE METHOD OF PRE-DRYING A WET WEB OF TEXTILE FABRIC TO REMOVE FREE MOISTURE THEREFROM BY THE USE OF A HOLLOW, HONEYCOMB-SURFACED, CYLINDER ROTATABLY MOUNTED BELOW A BLOWER WITHIN AN ENCLOSURE, SAID METHOD COMPRISING THE STEPS OF: ADVANCING SAID WEB PROGRESSIVELY THROUGH SAID ENCLOSURE WITH A STRETCH THEREOF TRAINED AROUND ABOUT 350* OF THE HONEYCOMBED SURFACE OF SAID CYLINDER WHILE MAINTAINING SAID STRETCH IN INTIMATE CONTACT THEREWITH UNDER PREDETERMINED TENSION; AUTOMATICALLY REDUCING THE EFFECTIVE WIDTH OF SAID HONEYCOMBED SURFACE WITHIN THE INTERIOR THEREOF FROM THE EXTERIOR THEREOF TO CONFORM WITH THE WIDTH OF SAID WEB, WHILE SAID ROLL IS ROTATING; CONTINUOUSLY DISCHARGING AIR DOWNWARDLY FROM SAID BLOWER THROUGH SAID FABRIC STRETCH AND THROUGH SAID HONEYCOMBED SURFACE, INTO THE INTERIOR OF SAID CYLINDER; CONTINUOUSLY HEATING THE SAID AIR DISCHARGED FROM SAID BLOWER, TO A TEMPERATURE OF ABOUT 300*F. IN ADVANCE OF SAID FABRIC STRETCH TO LADEN THE AIR WITHIN SAID CYLINDER WITH FREE MOISTURE; CONTINUOUSLY WITHDRAWING SAID MOISTURE LADEN AIR FROM SAID CYLINDER AND RECIRCULATING A PREDETERMINED PERCENTAGE OF THE VOLUME THEREOF TO THE INTAKE OF SAID BLOWER; AND CONTINUOUSLY DISCHARGING A PREDETERMINED REMAINING PERCENTAGE OF THE VOLUME OF SAID MOISTURE LADEN AIR UNDER PRESSURE FROM THE PRESSURE SIDE OF SAID BLOWER, INTO AN ATMOSPHERE REMOTE FROM SAID ENCLOSURE. 